The present invention relates to a telecommunication system for register recall as defined in the preamble of claim 1, where the telecommunication system is e.g. a WLL system.
WLL system (WLL, Wireless Local Loop) refers to a system in which a subscriber is connected to a telephone network via a wireless link system. The subscriber interface is achieved using special terminal equipment. In principle, the terminal equipment functions like a known mobile telephone, but it can be assigned a limited mobility area within which it can function. To implement the wireless link system, mobile communication technology, e.g. GSM technology (GSM, Global System for Mobile Communications) can be applied.
Open interfaces (V5.1 and V5.2) between an access node and a local exchange are defined in ETSI (European Telecommunications and Standards Institute) standards of the ETS 300 324 and ETS 300 347 series. V5 interfaces enable subscribers belonging to a physically separate access network, either wired or wireless, to be connected using the standard interface of the telephone exchange. The V5.2 interface supports analogue telephones as used in the public telephone network, digital subscriptions, such as ISDN (Integrated Services Digital Network) basic and system subscriptions as well as other analogue or digital terminal equipment based on semi-fixed connections.
In a WLL system, the subscriber""s terminal equipment may consist of a portable mobile station. The GSM network contains no function that could be used to activate register recall. A register is a device in the exchange that receives the numbers dialled by the subscriber and controls the subsequent connecting functions. Register recall means that the subscriber reserves the register again during a call to use a function. In an analogue system, register recall is typically effected by pressing the R or Recall key or equivalent. In the digital GSM mobile communication system, this function does not exist. When a WLL system is connected to the public telephone network via a V5 interface and the subscriber port type in the V5 interface is analogue subscriber, register recall cannot be activated if the terminal equipment used is a digital mobile station, especially when the terminal equipment used is a normal mobile station in a digital mobile communication network. e.g. the GSM network.
The object of the present invention is to disclose a new type of system that can be used to eliminate the above-mentioned drawback. A specific object of the invention is to achieve a system that allows the utilisation of analogue network services using digital terminal equipment, especially a normal mobile station in a digital mobile communication network, e.g. the GSM network.
As for the features characteristic of the present invention, reference is made to the claims.
The system of the invention comprises a local exchange and an access node connected to the local exchange via a V5 interface. Connected to the access node is a wireless link system and further via the wireless link system a terminal device.
The system of the invention comprises elements by means of which a request to set the current call into hold state is sent from the terminal equipment to the access node. The access node sends the terminal equipment a response message rejecting the request. The access node sends a register recall request to the local exchange via the V5 interface.
In a preferred embodiment of the invention, the request from the terminal equipment to the access node to set the current call into hold state is sent as a HOLD message consistent with the wireless link system. The HOLD message is described in GSM standard 04.08.
In a preferred embodiment of the invention, the access node resects the request from the terminal equipment to hold the current call by sending a HOLD REJECT response message consistent with the wireless link system. The HOLD REJECT message is described in GSM standard 04.08.
In a preferred embodiment of the invention, the request from the access node to the local exchange is sent as a SIGNAL message consistent with the wireless link system. Preferably the Pulsed-signal information element of the SIGNAL message has the value Register recall. The SIGNAL message is described in ETSI standard ETS 300 324-1.
In a preferred embodiment of the invention, the wireless link system used is based on a digital mobile communication system, preferably the GSM system.
The invention provides the advantage that it allows the users of portable terminal equipment to use analogue network subscriber functions as transparently as possible. A further advantage is that it makes it possible to use portable terminal equipment of the public GSM network in a WLL system.